Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 310013
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
813 PM EDT MON MAY 30 2016
The remnants of tropical system Bonnie will slowly lift northeast
along the Carolina Coast over the next couple of days. Moisture will
increase ahead of a cold front approaching from the northwest
Thursday and Friday. The front will move through the region on
Saturday but likely stall nearby over the weekend.
.NEAR TERM /THROUGH TUESDAY/...
As of 810 pm, KGSP and TCLT radars indicated a broken line of
showers and thunderstorms from the GSP area north across the Unifour
of NC. Recent CAMs show the activity drifting east across the
foothills and Piedmont through the remainder of the evening. I will
update the forecast to adjust the timing and placement of PoPs.
As of 6 pm, widely scattered showers and thunderstorms continue
across the upper Savannah River Valley. I will update the forecast
to increase PoPs along the SC/GA line. Otherwise, the current
forecast appears in good shape.
As of 130 PM: Cumulus have grown over the mountains in the past
90 minutes or so, and showers are now seen on radar over SW NC
and on the Blue Ridge north of I-40. This appears to agree with
most of the meso guidance, and following them, the expectation
remains that this activity will gradually propagate southeastward
into the upper Piedmont. Further upstream, discrete convection is
lining up along a weak boundary near the KY/WV/VA borders. While
these cells will gradually spread south, it appears unlikely they
will reach the NC Mtns before late afternoon, if they survive that
long. We`ll keep an eye on that activity over the next few hrs.
The remnants of former tropical cyclone Bonnie will remain invof
the "Grand Strand" into Tuesday morning, before beginning a gradual
northeastward movement by the end of the day. With the low remaining
on our periphery, northeasterly low level flow will continue over
our CWFA. This will provide enhanced moisture as well as very weak
convergence, which could allow some shower activity to persist
overnight. Plus, morning stratus is expected to develop over the
eastern third of the CWFA. Elsewhere, only cirrus are expected to
be seen overnight, and with winds remaining light, patchy fog is
expected to develop in some areas. Notable visibility restrictions
currently are not anticipated. Mins tonight will be a category or
two above normal.
Despite Bonnie and the boundary sagging southward from KY/VA,
diurnally driven instability will be the main justification for
PoPs. Meso models (namely 4km NAM Nest and the NCEP HiRes WRFs)
depict most activity firing over the higher terrain Tue aftn,
though uncapped profiles are seen over the most of the Piedmont
as well. Hence a mentionable PoP extends throughout the area Tue,
with the best chances along the Blue Ridge once again. Very weak
shear will lead to discrete convection, producing mainly isolated
heavy rainfall and perhaps a few strong gusts.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 215 PM Monday: The remnant Bonnie circulation will lift slowly
northeast along the North Carolina coast Wednesday and Thursday.
Warm and humid air will remain in its wake across the western
Carolinas and northeast Georgia. Scattered, mainly diurnal
convection is expected Wednesday, with best coverage favoring the
mountains. Coverage increases on Thursday with the trend remaining
mainly diurnal and best coverage across the mountains. although
moderate instability is forecast both days, there is very little
shear. This along with moist vertical profiles should limit the
severe thunderstorm potential. However, he light steering flow up
the column will create a heavy rain threat with any thunderstorms
that form. Highs will be up to 5 degrees above normal with lows up
to 10 degrees above normal.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 215 PM EDT Monday: the medium range fcst picks up at 00z on
Friday with upper ridging off to our east and a southern stream
upper low beginning to cut off over Texas. Over the next couple of
days, this low remains nearly stationary as steep upper ridging
builds over the Western CONUS. By the latter half of the weekend, a
broad upper trof begins to dig down over the Great Lakes as
impressive ridging persists to the west.
At the sfc, a weakly forced cold front will be moving into the CWFA
by early Friday as the remnants of Bonnie finally dissipate off the
NC Coast. The overall sfc pattern is expected to remain weakly
forced with the cold front stalling out over the region late Friday
and Sat. As we approach the end of the period another cold front
will likely develop and move thru the fcst area sometime late Sunday
into Monday with significant differences still apparent between the
long range models. As for the sensible fcst, no major changes were
needed with solid to low end likely chances for numerous showers and
ts each day/evening. Some drying is expected by the end of the
period early next week, however it is not clear exactly how quickly
that second front will move thru the area. Temps will start out just
above climatology and cool a few degrees on Sunday and Monday.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: KGSP and TCLT radars indicated a broken line
of showers and thunderstorms from the GSP area north across the
Unifour of NC. Recent CAMs show the activity drifting east across
the foothills and Piedmont through the remainder of the evening. I
will use TEMPO to highlight the passage of the convection. Late
tonight, the primary concern will be the formation of fog and low
clouds over wet ground. I will indicate more fog coverage as seen in
the 23z LAMP guidance, generally going with MVFR fog with MVFR to
IFR ceilings east. NE winds are forecast to continue across the
region on Tuesday, ranging from 6 to 9 kts. Mtn ridge thunderstorms
are expected to develop around 18z to 19z, drifting east of the mtns
during the late afternoon and early evening.
Outlook: Bonnie`s remnant low is expected to move very slowly
up the coastal Carolinas over the next several days, maintaining
increased precip and morning stratus chances at KCLT. Otherwise,
patchy fog chances continue at KAVL each morning, with scattered
afternoon/evening SHRA/TSRA increasing in coverage throughout
during the week.
00-06Z 06-12Z 12-18Z 18-00Z
KCLT High 99% High 89% High 94% High 92%
KGSP High 100% High 94% High 87% High 100%
KAVL High 100% High 97% High 99% High 100%
KHKY High 100% High 95% High 99% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 88% High 97% High 100%
The percentage reflects the number of guidance members agreeing
with the schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: